Cutting Head for a Brush Cutter, Edge Trimmer or Similar

ABSTRACT

The invention relates to a cutting head for a brush cutter, edge trimmer or similar, the head being of the type including at least a passageway for a cutting string and a locking element of the cutting string. The cutting head is characterized in that the locking elements include at least one ratchet wheel, including a toothed wheel mounted in rotation around an axis in such a manner that said teeth project in the passageway. The ratchet can be arranged in such a way that the toothed wheel can turn in a given direction to allow the introduction of the cutting string in the passageway and cannot turn in the opposite direction, thereby locking the cutting string in the passageway.

The present invention relates in general to the field of spinning-string implements for cutting vegetation, such as mowers, trimmers, etc . . . and more particularly to the locking element in order to hold firmly the string relative to the rotary cutting head on which they are mounted.

Portable apparatus for cutting vegetation, comprising a heat engine or an electric engine at the end of a shaft, at the vicinity of a handle, said engine driving in rotation at a high speed, generally at a speed of several thousand rounds per minute, a cutting head holding one or a plurality of cutting strings. The or the plurality of cutting string extends more or less radially with respect to the axis of rotation under the effect of centrifugal force when the cutting head is droved in rotation.

There is essentially two kinds of cutting head having a locking element of the cutting string.

A first kind of cutting head includes a reel receiving a cutting string winded to the reel, said cutting string being progressively wind off as the cutting string wear away.

The second kind of cutting head includes a locking element of one or a plurality of cutting strings, of short length.

This locking element to hold a cutting string onto a cutting head usually comprises one or a plurality of string strand passageways formed by metallic or similar eyelets mounted on a peripheral surface of the head and through them respective strands of string emerged from the head, said strand of string comprising a stop.

Besides a high production cost induced by the stop, it is difficult to replace such a cutting string onto this kind of cutting head in the course of use when the user is generally wearing gloves.

To overcome this drawback, a lot of locking elements of the cutting string had been proposed.

Most of these locking elements of the cutting string strand comprises a moving locking element such as cam which is urged by a spring and/or by the centrifugal force generated during rotation of the head so as to exert pressure on the string, a supporting backing wall being provided opposite the locking element in order to hold the string locally captive between the element and the supporting wall. Documents U.S. Pat. No. 4,301,642, U.S. Pat. No. 4,355,510, and EP-A-0 824 854 give examples of those locking elements.

To improve the locking effect, it is also known to provide the locking element with a series of teeth capable of anchoring better in the material of the string (generally made of polyamide).

Documents EP 1 416 786 and U.S. Pat. No. 6,928,741 show a locking element comprising a cam provided with teeth and cooperating with a spring.

Said teeth provide a better locking effect of a smooth cutting string strand but are inoperative for a toothed cutting string as disclosed in the european patent application 1 422 990 filed by the applicant and marketed under the Trademark FLEXIBLADE®.

One of the objects of the invention is thus to remedy these drawbacks by proposing a cutting head for a brush cutter, edge trimmer or similar of type comprising at least one cutting string strand passageway and a locking element of said cutting string of simple design, low cost and achieving the locking of smooth and/or toothed cutting string strand.

To this end, and in accordance with the invention, there is proposed a cutting head for a brush cutter, edge trimmer or similar, the head being of the type including at least a passageway for a cutting string and a locking element of said cutting string, said cutting head is noteworthy in that said locking element are at least one ratchet wheel including on the one hand, a toothed wheel mounted in rotation around an axis in such a manner that said teeth project in the passageway, and on the other hand a ratchet arranged in such a way that the toothed wheel can turn in a given direction to allow the introduction of the cutting string in the passageway and can not turn in the opposite direction to lock the cutting string in the passageway.

Said ratchet includes preferably a cam pin mounted pivoting around an axis whose distal end can lodge itself between two successive teeth of the toothed wheel, and cooperating with a return spring of said the cam pin to maintain said cam pin between two successive teeth of said toothed wheel.

The return spring is a coiled spring extending in a blind hole of the cutting head, the end of the coiled spring leaning against the bottom and respectfully the median part of cam pin, said cam pin being for example a parallelepiped rod.

The toothed wheel comprises between 9 and 15 teeth and preferably 12 teeth.

Moreover, teeth of the toothed wheel have a complementary shape to the teeth shape of a toothed cutting string introduced in the passageway.

Said teeth of the toothed wheel have a straight edge or a concave edge, the concavity of teeth edges having a curvilinear shape or a generally V-shape.

In another embodiment, each toothed wheel comprises a central hole with an oblong shape, the axis extending into said central hole in such a manner that cutting string strand of different sizes can be introduced in the passageway zone.

Finally, said cutting head comprises two parallel passageways extending symmetrically on both sides of the rotation axis of the cutting head, each passageway including a ratchet wheel.

Further advantages and characteristics will become more apparent from the following description of a plurality of variant embodiments that are given by way of nonlimiting examples of the cutting head for a brush cutter according to the invention, with reference to the appended drawings, in which:

FIG. 1 shows in perspective a brush cutter including a cutting head according to the invention,

FIGS. 2 à 4 are three views in side elevation illustrating a cutting head according to one embodiment of the invention,

FIG. 5 is a schematic plan view of a generally disc-shaped intermediate part that form a part of the cutting head according to the invention comprising a locking element of a cutting string strand,

FIG. 6 is a view in cross-section along the line III-III of the locking element illustrated in FIG. 2.

It will be noted as a preliminary matter that, from one figure to the other, the identical or similar elements or parts have, wherever possible, been identified by the same reference marks.

With reference to FIG. 1, a brush cutter usually comprises a shaft 5 including handles 10 and an electric or heat engine 15 driving a drive shaft 20, a cutting head 25 being mounted at the distal end of said drive shaft 20.

FIGS. 1 to 3 represent a cutting head 25 for a brush cutter, edge trimmer and similar according to the invention, suitable for being mounted on the extremity of a drive shaft 20 provided for the purpose, fixing arrangements 30 such as washer, nut, mechanism of indexation in rotation, as well as a counterplate 35 intended to cooperate with the said fixing arrangements in a manner completely conventional in itself.

The cutting head 25 is implemented here by overlaying and assembling two disc-shaped parts 100 a and 100 b concentric with the axis of rotation of the drive shaft 20. Each disc-shaped part 100 a and 100 b comprises, on their faces turned one towards the other, arrangements for running of strands of string and for retaining those strands as will be seen in detail below.

FIG. 2 illustrates the cutting head 25 before assembly to the shaft 20, whereas FIGS. 3 and 4 illustrate, respectively in a view with partial cutaway and a view in elevation, the cutting head 25 mounted on the shaft 20.

With reference now to FIG. 5, this shows a disc-shaped part 100 contributing to the implementation of the cutting head and including arrangements for retaining cutting string strands. It will be noted that this disc-shaped part 100 can be one of the parts 100 a and 100 b in FIGS. 2 to 4. Said disc-shaped part 100 is provided with a central orifice 105 through which the drive shaft 20 can pass.

This disc-shape part 100 comprises a set of bevels, outer bevels 110 and 115 and a central bevel 120 delimiting internally the portions of the part that are raised and externally the portions of the part that are recess. The overall contour of the bevels is here circular and follows the contour of the disc, set back at a certain distance from this contour.

Bevels 110,1115 extend in a rectilinear and adjacent manner the one to the other to delimit a first zone 125 of cutting string strand passageway 130, this passageway opening onto the outside at a first opening 135 and a second opening 140, for the outlet of a strand of a cutting string 130. The axis A along which the zone 125 of cutting string strand passageway 130 extends is situated a certain distance, marked D, from the centre C of the disc-shaped part 100, i.e from the centre C of the central orifice 105, in such a way that the cutting string strand 130 does not extend radially from the cutting head 25.

Moreover, the disc-shape part 100 also comprises, on a section of the string strand passageway zone 125, arrangements for retaining cutting string strands 130. These retaining arrangements are a ratchet wheel 145 including on the one hand, a toothed wheel 150 mounted in rotation around an axis 155 in such a manner that said teeth project in the zone of passageway 125, and on the other hand a ratchet 160 arranged in such a way that the toothed wheel 150 can turn in a given direction to allow the introduction of the cutting string strand 130 in the passageway 125 and can not turn in the opposite direction to lock the cutting string strand 125 in the passageway 130.

The toothed wheel 150 extends in a cavity 165 formed in the disc-shape part 100, opened into the passageway zone 125 and communicating with a groove 170 in which the ratchet 160 extends, a blind hole 175 being opened into said groove 170, said blind hole receiving a return spring. The rotation axis 155 of the toothed wheel 150 is preferably parallel to the axis C of the central orifice 105 to reduce the size of the cutting head 25; Nevertheless, it is quite obvious that the rotation axis 155 of the toothed wheel 150 may present any orientation without thereby departing from the scope of the invention.

Said toothed wheel 150 comprises between 9 and 15 teeth, and preferably 12 teeth, having advantageously a complementary shape to the teeth shape of a toothed cutting string strand 130 introduced in the passageway zone 125. In this embodiment, the cutting string strand 130 has triangular teeth such as disclosed in the European patent application 1 422 990 filed by the applicant and marketed under the Trademark FLEXIBLADE®.

Said ratchet 160 includes a cam pin 180 mounted pivoting around an axis, whose distal end can lodge itself between two successive teeth of the toothed wheel 150, and cooperating with a return spring of said cam pin 180 to maintain said cam pin 180 between two successive teeth of said toothed wheel 150. The cam pin 180 is a globally parallelepiped rod and the return spring is a coiled spring 185 extending in the blind hole 175 of the cutting head 25, the end of the coiled spring 185 leaning against the bottom and respectfully the cam pin 180, on this median part.

It is quite obvious the the ratchet 160 may be substituted for an equivalent ratchet without thereby departing from the scope of the invention.

When a toothed string strand 130 is introduced into the passageway zone 125 from the opening 135, teeth of said toothed string 130 cooperate with teeth of the toothed wheel 150 to drive it in rotation in the clockwise direction (FIG. 5), the ratchet 160 keeping free the rotation of the toothed wheel 150. When the cutting head 25 is droved in rotation, the centrifugal force tends to move out the cutting string strand from the passageway zone 125 trough the outlet 140. Then the ratchet 160 lock the rotation of the toothed wheel 150 in the anti-clockwise direction to retain the cutting string strand 130 into the passageway zone 125.

With reference now to FIG. 6, teeth of the toothed wheel 150 have a straight edge; nevertheless said teeth may have a concave edge, of a curvilinear shape or of generally V-shape, represented in dotted line in FIG. 6, to make easier the introduction and besides the locking of cutting string strand 130 with a circular or squared cross-section or similar.

More generally, any recessed profile can be envisaged at the level of the teeth of the toothed wheel 150 to better receive the string, irrespective of the shape of the cross-section of the latter.

In another embodiment, with reference to FIG. 5, the toothed wheel 150 comprises a central hole 190 with an oblong shape, represented in dotted line, axis 155 extending into said central hole 190 in such a manner that cutting string strand 125 of different sizes can be introduced in the passageway zone 125. In this way, the toothed wheel can slide along the oblong central hole 190 in function of the diameter of the cutting string strand 130 introduced into the passageway zone 125.

Finally, FIG. 5 shows that the disc-shape part 100 comprises, with a symmetry of revolution of 180° relative to the arrangements described above, some second passageway, bearing and locking arrangements for a second strand of string, these arrangements being indicated by the same reference marks plus a “prime” mark. In this manner, the cutting according to the invention, comprises two parallel passageways 125,125′ extending symmetrically on both sides of the rotation axis C of the cutting head 25, each passageway 125,125′ including a ratchet wheel 145,145′.

Moreover, it is quite obvious that the cutting head may have arrangements including retaining arrangements as disclosed above to provide a cutting head comprising an upper level with two string strands with diametrically opposed outlets, and a lower level with two other string strands with diametrically opposed outlets also, but offset by 90° in relation to the first ones.

Naturally, the present invention is not limited to the embodiments described and represented, and those skilled in the art will be able to provide many variants and modifications. 

1. A cutting head for a brush cutter or edge trimmer, the head being of the type including at least a passageway for a cutting string and a locking element of said cutting string, wherein said locking element comprises: at least one ratchet wheel including, a toothed wheel mounted in rotation around an axis in such a manner that the teeth project in the passageway; and a ratchet arranged in such a way that the toothed wheel can turn in a given direction to allow the introduction of the cutting string in the passageway and cannot turn in the opposite direction to lock the cutting string in the passageway.
 2. The cutting head according to claim 1 wherein said ratchet includes a cam pin configured to pivot around an axis, wherein the distal end of the cam pin can lodge itself between two successive teeth of the toothed wheel and cooperate with a return spring of said cam pin to maintain said cam pin between two successive teeth of said toothed wheel.
 3. The cutting head according to claim 2 wherein the return spring is a coiled spring having a first end and a second end, the coiled spring extending in a blind hole of the cutting head, the first end of the coiled spring leaning against the bottom of the blind hole and the second end of the coiled spring leaning against the cam pin.
 4. The cutting head according to claim 2 wherein the cam pin is a parallelepiped rod.
 5. The cutting head according to claim 3 wherein the coiled spring leans against the median part of the cam pin.
 6. The cutting head according to claim 1 wherein the toothed wheel comprises between 9 and 15 teeth.
 7. The cutting head according to claim 6 wherein the toothed wheel comprises 12 teeth.
 8. The cutting head according to claim 1 wherein the teeth of the toothed wheel have a complementary shape to the teeth shape of a toothed cutting string introduced in the passageway.
 9. The cutting head according to claim 1 wherein the teeth of the toothed wheel have a straight edge.
 10. The cutting head according to claim 1 wherein the teeth of the toothed wheel have a concave edge.
 11. The cutting head according to claim 10 wherein the concavity of the teeth edges have a curvilinear shape.
 12. The cutting head according to claim 10 wherein the concavity of the teeth edges have a generally V-shape.
 13. The cutting head according to claim 1 wherein each toothed wheel comprises a central hole having an oblong shape, an axis extending into said central hole in such a manner that cutting string strands of different sizes can be introduced into the passageway zone.
 14. The cutting head according to claim 1 further comprising two parallel passageways extending symmetrically on both sides of a rotation axis C of the cutting head, each passageway including a ratchet wheel. 